Ablation of cardiac tissue is well known as a treatment for cardiac arrhythmias. In radio-frequency (RF) ablation, for example, a catheter is inserted into the heart and brought into contact with tissue at a target location. RF energy is then applied through electrodes on the catheter to heat tissue to a destructive temperature in order to create a lesion for the purpose of breaking arrhythmogenic current paths in the tissue.
Irrigated catheters are now commonly used in ablation procedures. Open-loop irrigation provides many benefits including cooling of the electrode and tissue which prevents overheating of tissue that can otherwise cause adjacent blood to form char and coagulum. Despite efficient cooling of the electrode tip, under certain circumstances, adjacent catheter tip structures are heated by the tissue lesion site and the formation of coagulum and/or char can occur on these structures which are typically formed from a non-electrically conductive elastomer or plastic. The historic mode of operation relies on a scavenging effect where the tip electrode cooling fluid also cools these adjacent structures to some degree. However, it is desirable for an irrigated ablation catheter to prevent the formation of char and/or coagulum on adjacent, non-ablating tip structures and surfaces by convective and direct cooling.
Accordingly, it is desirable that an irrigated ablation catheter provide efficient cooling of adjoining non-ablating catheter tip structures which, due to their close proximity, are heated by the tissue lesion site.